In recent years, display devices such as a liquid crystal display device and an organic EL display device have been developed which can provide high-quality display with a smaller thickness and lower power consumption. These display devices each include a display section that displays an image and a terminal section formed around the display section. The terminal section includes a plurality of protruding electrodes that are electrically connected to control lines for controlling the pixel portions of the display section. As the display section has higher resolution and smaller size, a pitch between the protruding electrodes disadvantageously decreases.
Moreover, variations in the amount of an applied organic EL material and degradation of the organic EL material cause an organic EL display device to emit light in varying amounts, leading to variations in luminance over the display section. In order to eliminate variations in luminance, feedback processing on a voltage and a current is necessary, resulting in a complicated driving circuit for driving a pixel portion of the display section. Thus, the number of control lines for controlling the pixel portions of a display section tends to increase as compared with a liquid crystal display device. Accordingly, a pitch between the protruding electrodes disadvantageously decreases.
To address this problem, a method of increasing a pitch between protruding electrodes by a staggered arrangement has been proposed (for example, see Patent Literature 1).
Specifically, as illustrated in FIG. 14A, a display device 10 includes a plurality of external circuits 30 around an insulating substrate 40. Flexible printed boards 50 are stacked on the insulating substrate 40. Flexible printed boards 60 are stacked over the respective flexible printed boards 50. The external circuits 30 are electrically connected to the insulating substrate 40 via the flexible printed boards 50 and 60.
As illustrated in FIG. 14B, the insulating substrate 40 includes a large number of electrodes 43 arranged at a predetermined pitch. The insulating substrate 40 further includes insulating films 41 and insulating films 42 that are alternately formed along the alignment direction of the electrodes 43 so as to partially cover the electrodes 43.
As illustrated in FIG. 14C, the flexible printed board 50 includes a large number of electrodes 51 formed at a pitch twice as large as the predetermined pitch. The flexible printed board 60 includes a large number of electrodes 61 formed at a pitch twice as large as the predetermined pitch. The electrodes 43 exposed outside the insulating films 42 are connected to the electrodes 51. The electrodes 43 exposed inside the insulating films 41 are connected to the electrodes 61.